We are investigating (1) the relationship of genetic recombination to DNA repair-defectiveness in strains of yeast selected for hypersensitivity to methyl methanesulfonate, (2) the relationship of genetic recombination to the mating-type locus, (3) the regulation of translation as revealed by studies of supersuppressors and their modifiers, and (4) gene mapping and what this reveals about chromosome structure. BIBLIOGRAPHIC REFERENCES: Mortimer, R. K. and D. C. Hawthorne (1975) Genetic mapping in yeast. Methods in Cell Biology, Vol. XI pp. 221-233.